Oven liner ground connection

ABSTRACT

An electrical grounding arrangement for an oven liner in which a ground connection washer is provided having a tapering tab projecting generally perpendicular of the plane of the remainder of the washer and which is sized so that as the anchor bolt for the oven liner is pulled tight, the edges of the root of the tab are driven into interfering engagement with the hole in the range body back liner through which the anchor bolt projects, so that the edges of the tab break through oxides and enamel at the edge of the hole to provide positive ground contact.

United States Patent Pankow 1 Sept. 19, 1972 [54] OVEN LINER GROUND CONNECTION [72] Inventor: Edmund G. Pnnkow, Mansfield,

Ohio

[73] Assignee: Westinghouse Electric Corporation,

Pittsbugh, Pa.

[22] Filed: May 11, 1971 [21] Appl. No.2 142,306

[52] US. Cl ..339/14 R, 339/96, 174/51, 85/16, 219/414 [51] int. Cl. .1101! 13/34 [58] Field 01 Search ..174/51, 78, 35 MS; 339/14, 339/14 L, 17, 14 R, 95 R, 95 ST, 96; 85/16;

[56] References Cited UNITED STATES PATENTS 3,435,126 3/1969 Hamilton ..l74/78 1,380,738 6/1921 Raebum ..85/l6 2,061,372 11/1936 Wallin ..85/l6 X 2,157,188 5/1939 Robinson ..339/95 T 3,065,442 11/1962 Hubbell et a1 ..339/95 R 3,486,158 12/1969 Softysik et a1 ..339/l4 L 3,594,490 7/ 1971 Mitchell et al. ..174/35 MS FOREIGN PATENTS OR APPLICATIONS 552,224 l/1958 Canada ..174/51 1,034,739 4/1955 Germany ..174/51 Primary Examiner-Volodymyr Y. Mayewsky Att0meyF. 1-1. Henson and E. C. Arenz 57] ABSTRACT An electrical grounding arrangement for an oven liner in which a ground connection washer is provided having a tapering tab projecting generally perpendicular of the plane of the remainder of the washer and which is sized so that as the anchor bolt for the oven liner is pulled tight, the edges of the root of the tab are driven into interfering engagement with the hole in the range body back liner through which the anchor bolt projects, so that the edges of the tab break through oxides and enamel at the edge of the hole to provide positive ground contact.

4 Claims, 6 Drawing Figures PATENTEDSEP 19 I972 FIG.5.

FIG.6.

OVEN LINER GROUND CONNECTION BACKGROUND OF THE INVENTION 1 Field of the Invention The invention pertains to the art of providing electrical grounds for oven liners.

2. Description of the Prior Art Good product safety practice requires that the liner of a cooking oven be grounded permanently to the electrically grounded metal body of the range or outer shell of the oven. One usual way of effecting this ground is to apply a serrated-edge spring type washer to the outer end of the anchor bolt which extends between the oven liner and the range back liner. The nut which is used to pull the anchor bolt up tightly also causes the serrations to cut through the ground coat enamel and oxide of the range back liner and provide the contact necessary for grounding. Such serrated washers, and other clamps, grounding clips and connectors utilizing se rrated edges or faces for obtaining a grounded engagement with a metal wall are shown for example in US. Pat. Nos. 3,486,158, 3,065,442, and 2,508,655. Some of these devices, including ordinary serratededge spring type washers, are relatively sophisticated and expensive.

Accordingly, the aim of my invention is to provide a ground connection device which is relatively inexpensive but highly effective.

SUMMARY OF THE INVENTION In accordance with my invention, a relatively low cost ground connection arrangement for an oven liner is provided with a one-piece washer member which includes a tapered tab portion turned generally perpendicularly out of the plane of the remainder of the washer and which leaves a correspondingly shaped, generally centered aperture through which the anchor bolt from the oven liner projects. The tab has a width at its root which is designed to slightly exceed that chordal dimension of the hole that the tab extends across as installed. Thus, the edges of the root of the tab engage the edges of the hole in an interference fit when the nut for the anchor bolt is tightened down. Accordingly, the tapered root edges of the tab break through any oxides and enamel at the edges of the hole to provide the positive ground contact desired.

DRAWING DESCRIPTION FIG. 1 is an exploded isometric view of an oven liner, anchor bolt, and a fragmentary portion of the range body back liner before the parts are assembled;

FIG. 2 is an isometric view of the ground connection washer;

FIG. 3 is a fragmentary vertical sectional view of the assembled arrangement;

FIG. 4 is a face view corresponding to one taken along the line IV-IV of FIG. 3 and illustrating the relationship of the tab where it extends diametrically across the hole in the range body back liner;

FIG. 5 is a view similar to FIG. 4 but illustrating an arrangement in which the tab extends across a chord of a circular hole in the back liner where the chord is not the diameter of the hole; and

FIG. 6 is a view similar to FIGS. 4 and 5 but illustrating a modification in which a rectangular hole is used in the body back liner.

DESCRIPTION OF THE PREFERRED EMBODIMENT The open-face oven liner 10 of FIG I is shown with numerous details omitted and with the general structure of the range which encompasses the oven liner also omitted. The oven liner includes a pair of opposite side walls 12, each of which has a bracket 14 attached to the rear margin of the side walls at an intermediate height. When the oven liner is assembled to the remainder of the range body, an anchor bolt 16 with a hook-shaped end is hooked in the hole of the bracket with the opposite threaded end of the anchor bolt being received in aligned opening 18in the range back liner 20.

The washer 22 (FIG. 2), which is the heart of this invention, is then applied to the threaded end of the anchor bolt 16 and the nut 24 is then turned onto the threaded end and turned to pull the oven liner 12 rearwardly by means of the anchor bolt and to drive the tab 26 of the washer into the opening 18 of the body back liner.

The perimetric flange 28 (FIG. 1) of the oven liner abuts against other range structure to limit the rearward movement of the oven liner during tightening of the nut 24 on the bolt 16. Thermal insulation 30 is located between the rear wall of the oven liner and the body back liner. It will be appreciated that one anchor bolt is used on each side of the oven liner. Also, the means for securing the anchor bolt to the oven liner may take other forms than the bracket shown.

Referring again to FIG. 2, the washer 22 can be made of cold rolled steel with the tab 26 having the generally tapered and triangular form shown and being lanced out of the general center of the washer. The tab is substantially planar and extends generally perpendicularly to the remainder of the washer, and leaves a hole 32 in the general center of the washer which corresponds to the shape of tab 26. The root 34 of the tab is that portion which is closely adjacent to the face of the washer presented to the viewer in FIG. 2. Because of the lancing operation, this portion of the tab has less taper at its opposite edges than the remainder of the tab.

In accordance with the invention, the root 34 of the tab is sized to have an interference fit with the hole 18 in the back liner so that in tightening down the nut upon the anchor bolt the edges of the root 34 engage the edges of the hole with a sufficient interference fit that the tab edges break through any oxides and enamel at the edge of the hole 18 to provide the positive ground contact desired. The interference fit also results in the washer remaining tightly in place against the body back liner even though the bolt should relax a bit, or the nut loosens slightly.

FIG. 4 shows the currently preferred arrangement for utilizing the invention. The aperture 18 in the back liner is sized so that its diameter is slightly less than the width of the root 34 of the tab so that in applying the washer to the back liner the tab extends diametrically across the hole 18. With this arrangement the diameter of the bolt 16 is not critical since the tab is self-centered in the hole 18.

In another arrangement as shown in FIG. 5, the tab 26 is not centered in the hole 18, but the bolt 16 diameter is selected so that the tab is held in a forced over position to the side of a diameter of the hole 18 by virtue of the bolt 16 engaging against the edges forming the aperture 32 in the washer.

In FIG. 6, a rectangular hole 36 is provided in the back liner and the tab 26 is arranged in the rectangular hole adjacent one of the legs of the rectangle. Again the bolt 16 diameter is selected to occupy substantially all of the remainder of the space between the one face of the tab and the opposite leg of the rectangle so that the tab cannot be assembled in a canted relation in the rectangle. In each of the arrangements of FIGS. 4-6, it may be said for purposes of this application that the root of the tab occupies a chordal position in the hole, which chordal dimension is slightly less than the width dimension of the root so that the proper interference fit is achieved.

The tapered shape of the tab illustrated is the preferred shape in that it facilitates the assembly and is relatively inexpensive to produce. The electrical resistance in the connection between the tab and the body liner is required to be less than 0.5 ohms by Underwriters Laboratory. Preliminary testing of the arrangement of the invention yields resistances of 0.01 ohms.

I claim as my invention:

1. A ground connection arrangement for making a ground connection between a metal oven liner anchor bolt secured to and electrically connected to a metal oven liner, and a metal back liner having a hole through which said anchor bolt projects, said arrangement including a nut, and a one-piece metal washer member including a tapered tab portion turned generally perpendicula'rly out of the plane of the remainder of said washer and leaving a correspondingly shaped, generally-centered aperture through which said anchor bolt projects, said tab having a width at its root slightly exceeding that chordal dimension of said back liner hole that said tab extends across as installed so that the edges of said root of said tab engage the edges of said hole in an interference fit when said anchor bolt is tightened by turning said nut onto said bolt, whereby said tab breaks through oxides and enamel at the edge of said hole to provide positive ground contact.

2. A ground connection arrangement according to claim 1 wherein said tab is substantially planar.

3. A ground connection arrangement according to claim 1 wherein:

said back liner hole has a diameter slightly less than the width of said root, so that said tab is self-centering in the diameter of said hole.

4. A ground connection arrangement including a metal washer and a grounded metallic panel to which the washer is applied to make the ground connection therebetween, said panel including a hole of a given chordal dimension, a metal member having a threaded end extending through said hole, and its opposite end secured to and electrically connected to another metallic member, and a nut for tightening said threaded member to press said washer against said panel, said washer having a tapered tab turned out of said washer generally perpendicularly, said tapered tab having a root portion of a width exceeding said chordal dimension sufficiently that as said washer is pressed against said panel the edges of said root engage in an interference fit with the edges of said hole and break through any coating at the edges of said hole so that said engagement provides a low resistance ground connection. 

1. A ground connection arrangement for making a ground connection between a metal oven liner anchor bolt secured to and electrically connected to a metal oven liner, and a metal back liner having a hole through which said anchor bolt projects, said arrangement including a nut, and a one-piece metal washer member including a tapered tab portion turned generally perpendicularly out of the plane of the remainder of said washer and leaving a correspondingly shaped, generally-centered aperture through which said anchor bolt projects, said tab having a width at its root slightly exceeding that chordal dimension of said back liner hole that said tab extends across as installed so that the edges of said root of said tab engage the edges of said hole in an interference fit when said anchor bolt is tightened by turning said nut onto said bolt, whereby said tab breaks through oxides and enamel at the edge of said hole to provide positive ground contact.
 2. A ground connection arrangement according to claim 1 wherein said tab is substantially planar.
 3. A ground connection arrangement according to claim 1 wherein: said back liner hole has a diameter slightly less than the width of said root, so that said tab is self-centering in the diameter of said hole.
 4. A ground connection arrangement including a metal washer and a grounded metallic panel to which the washer is applied to make the ground connection therebetween, said panel including a hole of a given chordal dimension, a metal member having a threaded end extending through said hole, and its opposite end secured to and electrically connected to another metallic member, and a nut for tightening said threaded member to press said washer against said panel, said washer having a tapered tab turned out of said washer generally perpendicularly, said tapered tab having a root portion of a width exceeding said chordal dimension sufficiently that as said washer is pressed against said panel the edges of said root engage in an interference fit with the edges of said hole and break through any coating at the edges of said hole so that said engagement provides a low resistance ground connection. 